Assessment Comments
Assessment based on results of (1) IDNR/UHL biolgoical (REMAP) sampling in 2002 (Fish IBI= 48 (fair), BM-IBI= 61(good) and (2) IDNR/UHL biological (biocriteria) sampling in 2000 (Fish IBI= 51 (good); BM-IBI= 59 (good)).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" based on results of IDNR/UHL biological sampling in 2000 and 2002.
EXPLANATION: This assessment was based on data collected in 2000 and 2002 as part of the DNR/UHL stream biocriteria and REMAP projects, respectively. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 Fish IBI score was 48 (fair) and the BM-IBI score was 61 (good). The 2000 Fish IBI score was 51 (good) and the BM-IBI score was 59 (good). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The Fish IBI scores were slightly below the biological assessment criterion, which was determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
As part of the 2002 REMAP sampling project, stream physical habitat assessment found adverse conditions that are thought to contribute to the biological impairment. These include, bank instability, excessive silt deposition, and removal of riparian vegetation associated with livestock grazing. High silt levels were also observed during physical habitat assessment of the 2000 sample site.
